Usually, a magnetic bearing apparatus is used for the primary purpose of realizing ultrahigh speed rotation which is hardly realized by a rolling bearing apparatus that is conventionally widely used. As compared with a rolling bearing apparatus, in a magnetic bearing apparatus, ultrahigh speed rotation is enabled, but it is usual that the main unit of the bearing apparatus generates a large amount of heat because of an increased number of electrical components. In a conventional countermeasure for cooling a magnetic bearing apparatus, for example, air is supplied from the outside into a unit by a compressor or the like, and the supplied air flow is passed over the surface of a rotary shaft to conduct a cooling operation. Such a cooling structure for a magnetic bearing apparatus is disclosed in, for example, JP-A-8-61366.
In the above-described cooling structure, however, the air flow which is close to the ambient temperature is simply circulated from the outside into the unit. Therefore, the structure has problems in that the cooling performance is not excellent, and that apparatuses (such as a compressor) for supplying the air flow from the outside into the unit are additionally required and hence the scale of cooling facilities becomes large.